1. Field of the Invention
The present invention relates to a nerve stimulation device.
This application is based on Japanese Patent Application No. 2009-259911, the content of which is incorporated herein by reference.
2. Description of Related Art
Conventionally, there is known a treatment method that conducts defibrillation with energy lower than usual by stimulating a vagus nerve at the time of ventricular fibrillation of heart (convulsion condition of ventricle) (see, for example, Japanese Unexamined Patent Application, Publication No. Hei 8-38625). Japanese Unexamined Patent Application, Publication No. Hei 8-38625 also discloses installing a set of electrodes in a cervical region as an electrode for stimulating a vagus nerve.
There is known a cardiac treatment device having a set of electrodes for stimulating a vagus nerve that stimulates a vagus nerve when the cardiac rate is higher than a predetermined rate, and conducts cardiac stimulation rather than nerve stimulation when the cardiac rate is lower than the predetermined rate (see, for example, Japanese Unexamined Patent Application, Publication No. 2004-173790).
However, when contact resistance of an electrode to a nerve bundle increases with time due to adhesion of tissue or the like to the electrode, or when impedance increases due to disconnection of a lead wire or the like due to motion of living body, it is not possible to provide energy that is enough for an electric pulse to excite a nerve cell. In such a case, it may become difficult to continue the treatment of stimulating a vagus nerve with cardiac treatment devices disclosed in Japanese Unexamined Patent Application, Publication Nos. Hei 8-38625 and 2004-173790).